Listen, I love the booze more than anything, but there's no way I'm drinking a curdled shot, I don't care how much it looks like a delicious brain. I've been tricked into it before, and I'm definitely not doing it on purpose. But, if you insist on being grody:

Chill vodka for better smoothness. Add vodka and lime juice to a shaker, shake and strain into a shot glass. Using a straw, dip some Bailey's Irish Cream into the shot. Once you submerge the straw into the Bailey's put your finger on top of the straw to hold the Bailey's in the straw. Dip the straw tip into the vodka and slowly release your top finger. The Bailey's will curdle a little bit due to the lime juice and you should be able to make strands of Bailey's.

Repeat the straw/Bailey's process to build a "brain" in the shot glass. Add a splash of grenadine to the concoction to add the 'blood' to the mix. Down the hatch as a shot.

Alternatively, have a friend hold a shot of Bailey's in their mouth and then add one of lime juice and swish it around. Cement mixer! Puke! Lose a friend!